Children in nonsmoking families have higher levels of secondhand exposure if they live in multifamily dwellings. By Janet Raloff

Children who grow up in apartment buildings are more likely to inhale secondhand tobacco smoke than are kids living in detached homes, a new study finds — even if no one in their household ever lights a cigarette.

“This is the first study to show significant evidence of increased tobacco-smoke exposure among children who live in multi-unit housing,” reports pediatrician Jonathan Winickoff of the Massachusetts General Hospital for Children in Boston, who directed the study. Compared to children who grew up in detached houses, his team finds that those living in apartments excreted 45 percent more cotinine, which is a marker of nicotine exposure. The findings were released online December 13 in Pediatrics.

“Our new study is really the last link in the chain of evidence demonstrating the need for smoke-free buildings,” Winickoff says, “because it proves that children are absorbing that smoke.”

Overall, depending on the type of dwelling in which they lived, cotinine concentrations were quite low, averaging 0.053 to 0.075 nanograms per milliliter of urine among all 5,002 kids, aged 6 to 18. But a host of studies have linked even low-level exposures to behavioral changes and increased risk of allergy and asthma.

“The 2006 surgeon general’s report is clear: There’s really no safe level of secondhand smoke,” notes Gary Adamkiewicz of the Harvard School of Public Health, an environmental health scientist unaffiliated with the new research.

In the new study, Winickoff’s team examined data collected as part of the National Health and Nutrition Examination Survey conducted between 2001 and 2006 by the U.S. Centers for Disease Control and Prevention. Almost three-quarters of children excreted cotinine, including 84.5 percent living in apartments and 70 percent of those from detached homes. There was less than a 1 percent probability that the difference was due to chance. The prevalence of cotinine residues in children from attached homes fell in between.

The common occurrence of the smoke marker among children living in detached houses points to the importance of community exposures, Winickoff says. Kids may have been exposed by being near a parent's smoky clothing, by walking though doorways where smokers are clustered, riding in cars with a smoker or hanging out indoors where smokers previously have lit up.

While dramatic, the new findings hardly come as a surprise, since another recent study measured nicotine from tobacco smoke tainting the air in roughly 90 percent of 49 low-income apartments inhabited by nonsmokers.

“Our study confirmed on-the-ground evidence that folks who live in multi-family housing were reporting,” explains Adamkiewicz, an author of that study. People in nonsmoking residences often could smell smoke, which likely seeped in through ventilation systems, cracks around plumbing or under doors.

Concentrations that his team measured were low — “but not trivial,” he says. They were highest in those households where the residents had reported smelling smoke most frequently. By analyzing air movement in and out of an apartment, “we could calculate how many cigarettes someone would have had to have smoked to yield this level of nicotine in the air,” he says. “And in the apartments of nonsmokers, it started to approach a cigarette a day.” His team reported its findings in the December 2009 Tobacco Control.

The new study takes those results a step further, Winickoff says. “Although we now protect bartenders and people in restaurants in many places from secondhand smoke, we’ve forgotten to protect one critical segment: where children live.” But owing to the strong data that his team has just turned up, he says, “Landlords are soon going to be deciding not whether to go smokefree but how soon to go smokefree.”

And if they don’t, the Department of Housing and Urban Development may force the issue, says toxicologist Bruce Lanphear of Simon Fraser University in Vancouver, British Columbia. “You can’t ban smoking in private housing,” he acknowledges, “but HUD can ban smoking in public housing if there’s sufficient evidence to suggest that it’s in the best interest of kids’ health.”

Another reason the new study is important: It points to housing-related issues, Lanphear says, that at least on a population level may explain why kids in certain ethnic and low-income communities “have higher rates of wheezing or learning problems.”